1. Field of the Invention
The present invention relates to an ink ribbon for a printer, more particularly to an ink ribbon for an impact type printer for a computer, such as a wire dot printer or daisy wheel printer. The present invention also relates to an ink to be used for an ink ribbon for a printer, particularly a black ink to be used for an ink ribbon for a printer such as wire dot printer.
2. Description of the Related Art
Impact type printers such as wire dot printers or daisy wheel printers are now widely used, due to the increase in the use of computers and office automation. The cloth ink ribbons to be used in such printers usually comprise cotton cloth, silk cloth or nylon cloth as the base cloth, and contain an ink prepared by dissolving or dispersing dyes or colorants such as dyes in various solvents and coated on or impregnated in such a base cloth.
Cotton cloth, however, although having a good ink retentivity, has a problem of a lack of printing sharpness due to a thick cloth thickness. A silk cloth, although having a good ink retentivity and printing sharpness, has the problems of a poor durability and a high cost. On the other hand, the nylon fiber cloth now in use, although having an excellent durability, has a thickness as thick as 120 to 140 .mu.m. Accordingly, the problem that a sharply printed character cannot be transferred arises, and thus a sharp print is difficult to obtain even when the wire of the printing head is made finer.
Furthermore, in the prior art, soft dyes having absorption bands at visible regions of about 400 to less than 700 nm have been exclusively used, but these colorants have no absorption band at the near infrared region (700 nm to 900 nm), which is the wavelength of most bar codes now in use, and therefore, can not be used for that purpose.
Therefore, a hard pigment has been used in the prior art as the colorant having an absorption band in the infrared region (700 nm or higher) such as carbon black, black titanium oxide, or metal oxide, and accordingly, the wire of the printer was susceptible to abrasion by the hard pigment on which the wire is impacted through the ink ribbon. Also, this abrasion of the wire is caused by an adhering of the ink to the wire and a penetration of the hard pigment into the gap between the wire and the wire guide.
As described above, the ink ribbon for the impact type printer, such as a wire dot printer or daisy wheel printer, of the prior art has the problem of poor durability or printing sharpness and cannot cope with a high-speed operation of a printing head.
Various printers are widely used as the printing recording means of terminals of computers, etc., and various inks are used for the ribbons of printers such as a wire dot printer. The ink is impregnated in such printing ribbons, and particularly for black printing ribbons, a carbon black alone or together with, for example, a black oil-soluble dye such as nigrosine or aniline black, is used.
The black ink ribbon of the prior art as mentioned above contains carbon black as the colorant, and thus has problems such as an abrasion of the wire of the printer head or a generation of print blurring due to the presence of the black oil-soluble dye generally used therewith in combination. To maintain the blackness, sharpness and light resistance of a printed character, however, it is impossible to exclude a considerable amount of carbon black from the ink formulation for printer, and it has been necessary to formulate a black oil-soluble dye in a considerable amount to prolong the life of the ink ribbon by lowering the amount of carbon black formulated, to inhibit the abrasion of the wire while maintaining the print characteristics at as high a level as possible.